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Introduction

Images have always been a fundamental communication medium. The impressive
achievements in information technology of the last decade have brought images
to play a central role in computerized information systems, thus opening
an enormous application area. The amount of images stored and accessed in
electronic form is already very large, and is rapidly increasing. It is
expected that images will be a major content resource of digital libraries.

In this context, the ability to select from a large collection those
images that are relevant to a user request, specified either in visual or
in textual terms, is at the heart of the image retrieval problem, and, at
the same time, a fundamental functionality of a modern information retrieval
system. Queries expressed in visual terms (e.g., images themselves or elements
thereof) are handled on the basis of similarity criteria, and thus aim at
providing the user with images that "look like" the query; this
is "content-based image retrieval", a form of retrieval currently
being studied by the research community. On the other hand, queries expressed
in textual terms, such as natural language sentences or formal expressions
using a controlled vocabulary with a possibly complex syntax, address the
content of the images; this is known as "semantic content-based image
retrieval".

The fourth workshop of the DELOS working group addressed the topic of
"Image Retrieval" and was hosted by CNR in San Miniato, a small
medieval town not far from Pisa, from 28-30 August, 1997. DELOS is a Working
Group funded by the IT Long Term Research programme of the European Commission
to study and investigate existing and emerging technologies and issues relevant
to digital libraries.

The Workshop brought together 20 participants from eight different European
countries, as well as 6 invited speakers, one from Europe and 5 from the
United States. The workshop thus provided a significantly broad picture
of the research on image retrieval under way both in Europe and in the US.

The invited speakers' presentations addressed different aspects of the
image retrieval problem. In particular, Alberto Del Bimbo, from the University
of Florence, gave a comprehensive overview of content-based image retrieval.
Fang Liu from the MIT Media Lab illustrated a number of digital library
projects completed or in progress in the Vision and Modeling Group at the
MIT Media Laboratory. David Forsyth from the University of California at
Berkeley presented the results of a research project aiming at the retrieval
of pictures on the basis of the objects depicted. Simone Santini from the
University of California at San Diego investigated the problem of meaning
in image databases, arguing that the meaning of an image should be considered
as a result of the interaction between the user and the database, rather
than as an intrinsic property of the images. John Smith from the Image and
Advanced Television Laboratory of Columbia University presented a new approach
for automatically classifying images using both image features and related
text. He argued that the synergy of textual and visual information in Web
documents provides a great opportunity for improving the image indexing
and searching capabilities of Web image search engines. Olivia Frost from
the University of Michigan presented a project under way at her university
aimed at exploring the development and evaluation of multimode retrieval
schemes which employ both image and text and which are multiple path, iterative
and user-directed.

Other presentations from the European researchers ranged from modeling,
to the study of efficient access methods supporting similarity retrieval,
feature extraction methods and applications. In particular, Carlo Meghini
(IEI-CNR Pisa) presented an approach for combining syntax and semantics
in image retrieval, while Youssef Lahlou (GMD) described an object-oriented
model for semantic image indexing. The presentation of Roger Weber (ETHZ
Zurich) and Pavel Zezula (IEI-CNR Pisa) illustrated the problems related
to the definition of access structures for similarity retrieval in high
dimensional data spaces. Specific solutions were proposed. Roger Mohr (INRIA)
presented an approach to image retrieval that uses local characteristics;
Ines Oliveira (INESC Lisbon) illustrated a comprehensive set of image processing
techniques for video content extraction. Finally, Andre Csillaghy (ETHZ
Zurich) presented an application of image browsing and retrieval, applied
to astronomical archives.

These proceedings include extended abstracts of the talks given at the
Workshop.

We should like to that ESPRIT and ERCIM for supporting the Workshop,
and our collegue Tarina Ayazi, as well as the local people at San Miniato,
to make it happen.

Carlo Meghini

Pasquale Savino

The DELOS Working Group is a part of the ESPRIT Long Term Research Programme
(LTR No. 21057) and is managed by ERCIM (European Consortium for Informatics
and Mathematics)